1. Field of the Invention
The present invention relates generally to the field of commercial trucks and carts for carrying merchandise items such as various types of product containers. More specifically the present invention relates to a pallet jack with a pallet engaging fork having separate and independently movable first and second fork arms connected to independently controlled and operable first and second fork arm elevating means, for lifting a pallet loaded with a stack of items so that when the stack of items leans and is out of balance one fork arm can be elevated higher than the other to compensate and restore balance to the stack of items. The fork arm elevating means may be powered electrically, manually or by any other suitable power source. The first and second fork arm elevating means preferably include first and second hydraulic piston and cylinder assemblies drivably linked to first and second fork arm risers of conventional design. Each piston and cylinder assembly moves the corresponding fork arm riser linkages to lower fork arm wheels to elevate the corresponding fork arm and the corresponding side of a loaded pallet and to raise the fork arm wheels to lower the corresponding fork arm and the corresponding side of the loaded pallet. Apart from the fork arms being separate and independently raised and lowered by separate and independently controlled fork arm elevating means, the remainder of the pallet jack is conventional.
2. Description of the Prior Art
There have long been pallet jacks having pallet engaging lifting forks for lifting and transporting pallets loaded with containers of various products. Some pallet jacks have included hand powered hydraulic systems for elevating the lifting fork, while others have included electrically powered hydraulic systems. The lifting forks of all of these prior pallet jacks have had structurally interconnected fork arms, constraining the arms to move in unison. A problem with operating these prior pallet jacks has been that item loads on pallets are often stacked off center and off balance so that if the pallet remains level as it is lifted, the loads remain off balance and are likely to tip over while being transported.
It is thus an object of the present invention to provide a pallet jack which has separately elevatable lifting fork arms so that a pallet can be tilted while being elevated to compensate for a tilt and imbalance of a stack of items on the pallet.
It is another object of the present invention to provide such a pallet jack which alternatively can keep a pallet level while the pallet is lifted, where the load stacked on the pallet is adequately balanced.
It is still another object of the present invention to provide such a pallet jack which has lifting fork arms which can be separately raised and lowered under either manual power or electrical power.
It is yet another object of the present invention to provide such pallet jack design features which can be incorporated into a fork lift to achieve the same benefits.
It is finally an object of the present invention to provide such a pallet jack which is sturdy, relatively simple in design, reliable and easy to operate, and which is comparable in manufacturing cost to a conventional pallet jack.